shortest path algorithm

Hi,
I am trying to write a code to compute the shortest path between any two nodes in a graph. I wrote the code but the problem is that it is very slow when I run it for let us say 65 nodes (for every pair of nodes, the algorithm computes the shortest path). I saw on the internet that there are ways to do so, but they are very complicated codes. However, in my code, I use the Priority Queue built-in package so that I quickly extract the smallest value. Could you please help me in making the code fast?